Integration time for pp->bbjj +1jet Order_EW=4 at sqrt(s) = 100 TeV is ~8 days

[danilo.ferreiradelima@glasgow.ac.uk]

Dear Sherpa authors,

I have been trying to generate a sample of p p -> b b j j + 0/1 jet with Order_EW = 4; using CKKW for the merging. Its integration step has taken 4 days (for the b b j j + 1 jet integration) so far and Sherpa claims it will take at least 4 days more. This seems a bit unreasonable and I wonder if it is due to a mistake I am making or a bug.

The Run.dat file has been attached.

Best regards, Danilo

[danilo.ferreiradelima@glasgow.ac.uk]

Run card for pp->bbjj at sqrt(s) = 100 TeV (Order_EW=4) generation

[danilo.ferreiradelima@glasgow.ac.uk]

PS: Please note that this also happens with other similar processes (Order_EW=0 or 2 and with bbja, jbaa, etc), but for this process in particular it takes longer. For the other processes it can even take 2 or 4 days, which is still a lot, but not as worrying as 8 days.

[danilo.ferreiradelima@glasgow.ac.uk]

PPS: As a final note, I have also noticed that these messages happen often before the start of the integration:

Amplitude::GaugeTest(): Large deviation {

2.62003930531e-26

vs 2.62003930522e-26 => 3.16786596954e-11

}

..

Amplitude::GaugeTest(): Large deviation {

1.19412465114e-28

vs 1.19412465114e-28 => -3.60833585233e-12

}

.

Amplitude::GaugeTest(): Large deviation {

4.04840232988e-30

vs 4.04840232946e-30 => 1.03543840169e-10

}

.

Amplitude::GaugeTest(): Large deviation {

1.84506829698e-29

vs 1.84506829693e-29 => 2.65678590239e-11

}

[Stefan Hoeche]

Hi Danilo,

the gauge test warnings are unproblematic as long as the deviations shown are very small (order 1e-12 is ok, in some exceptional cases 1e-10 is also fine). To reduce integration time you may want to try a different scale choice, such as

   SCALES VAR{H_T2};

and/or consider parallelization via MPI (see the section on MPI in our Manual).

Best wishes Stefan